The shaking you describe sounds like something out of round/warped to me. This is more likely to be warped discs - this can happen with age and is not necessarily indicative of a fault. Replacing/up-rating them would sort this out. Although once upon a time I remember buying some front discs for my GTSt and they were warped to start with - they were a budget disc but I didn't expect them to be warped.
Just out of interest - is it 'disc' or 'disk'?